There are numerous ways to grab and hold of two dice. I have tried and used the five-finger grip, and the four-finger grip, and finally settled on the two-finger grip. For clarity and to satisfy the anatomy experts, the “thumb” is one of the necessary digits involved, in order to accomplish any of the grips, referring to fingers here, the thumb is understood. With that said, the two-finger grip is just one finger, the middle finger and one thumb. You cannot use two thumbs, as the rules state, only one hand on the dice.
I concluded that using only the thumb and middle finger was the best choice by deduction. Less leather on the surface of the dice meant less friction at the moment of release. It also reduced possible sticky fingers. It is true that the two-finger grip is a more delicate hold on the dice. It takes practice to develop the right amount of pressure.
No matter what grip you end up using, just be sure that it is one you are comfortable with, and that you are satisfied with your results.
For me, the five-finger grip, securely held the dice in my hand. I liked the feeling of a completely surrounded set in my clutch. However, my release was clumsy, and the dice flew through the air like wounded ducks.
I abandoned the five-finger grip and tried to master the four-finger grip. I got over my need to feel comfortable, trapping the dice from all sides. However, my issues with the four-finger grip were fitting my fingers comfortably on the forward faces, with the opposing thumb, and again, with the clean release. I struggled with a simultaneous release of my fingers. This caused one die to hook left or right. Additionally, I struggle with the pressure, keeping the dice together during the gripping process. My thumb pressure caused the set to gap at the front. Last, with my release, the times when my fingers left the dice together, was often ruined by my thumb, pushing through the dice, with the right die turning clockwise and the left dice turning counterclockwise.
Okay, this is why we practice at home and are reminded to practice, practice, practice.
The two-finger grip took practice and mental adjustments. Once I got it, my dice looked like two swans, matched in flight.
Great photos of different grips are here, at Dice Setter.
https://dicesetter.com/setting/mysets.htm
https://dicesetter.com/setting/stackingtopbottom.htm
Ed Jones